1. Field
The present disclosure relates generally to processing data, in particular, to generating simulated responses of a material to input. Still more particularly, the present disclosure relates to a method, apparatus, and computer usable program code for using virtual time reversal acoustics for structural health monitoring.
2. Background
Structural health monitoring techniques have been developed and used to monitor materials and structures. These techniques often build or incorporate the health monitoring systems directly into structures. These health monitoring systems may be used to determine whether changes have occurred over time to the structures and materials associated with the structure. For example, sudden changes in environments, such as electromagnetic effects, mechanical stresses, and other environmental effects may affect the integrity of various materials and structures over time. By having health monitoring systems built in to or associated with the structures to monitor the structures during use, appropriate measures and responses may be taken to prevent anomalies and failures and may prolong the life span of these structures.
A structural health monitoring system is typically implemented using a transmitter and a sensor configuration to transmit waveforms at various frequency ranges to an array of transducers and acquire data from the transducers' responses. Thus, a transducer may sometimes function both as a transmitter and a sensor.
An optimal waveform cannot be determined ahead of time because of the lack of information. As a result, a large number of input waveforms having different frequency ranges are used. Large amounts of data are recorded from the responses to prevent missing any information that may be needed. The need to use input waveforms or signals at different frequencies occurs because many parameters are present for optimization. For examples, these parameters include driving frequency, time duration, a number of cycles, window function for amplitude modulation, and other factors.
Time reversal acoustics is a method for focusing and analyzing waves for structural health monitoring. Time reversal acoustics has been used in medical imaging and recently introduced to structural health monitoring communities to identify an anomaly, such as, a tumor or damage to a structure. However, currently, this time reversal method requires sophisticated hardware setup and/or additional steps of actually time reversing and resending the transducer's response.
In other words, current time reversal acoustics involve sending a signal through a structure or medium using a transmitter. A sensor receives the response of the structure or medium to the transmitted signal. The sensor time reverses the received response and sends the time reversed response as a transmitted signal back to the original transmitter. The original transmitter receives the time-reversed transmitted signal and then performs run time reversal analysis on this time reversed received response.
The current method requires that a location from which a response to a signal is required, a transmitter or other device capable of receiving and transmitting the time-reversed signal is necessary. This requires additional hardware and collection of additional data sets. In addition, if the structural health monitoring is being performed on an array of transducers, a data set is collected for each path in the array of transducers. For example, if the array of transducers includes 26 transducers, a data set is collected for 26 times 25 (or 650) possible paths. In other words, to perform time reversal analysis on this array, 650 responses will be recorded and then each of the 650 responses are time reversed and sent out as drive signals for use in time reversal analysis.
The re-transmission and collection of the time reversed response requires additional sophisticated hardware and software. In addition, all of the additional re-transmitted time reversed response data collected by the different input signals are saved in the database. Thus, the amount of data collected is large and takes up a considerable amount of space in a structural health monitoring system.
Therefore, it would be desirable to perform time reversal analysis without actually re-transmitting time reversed signals through transducers and other hardware to reduce the amount of hardware required and the amount of data that has to be collected, saved, and/or retransmitted for a structural health monitoring system.